6-DoF tracking, also known as six degrees of freedom tracking, is a method by which a device (e.g. mixed-reality head-mounted device (HMD), robot, smartphone, etc.) uses sensors (e.g. cameras, inertial measurement units, etc.) to localize itself, or determine its position relative to its surrounding physical environment. When a device is turned on in a new environment, the device initially performs a coarse relocalization step, in which the rough vicinity of the current location of the device is determined, before the device performs a more fine-grained localization step to determine a more precise position of itself relative to its surrounding physical environment. For example, a mixed-reality HMD or smartphone can use this positional understanding to place holograms or digital content so as to appear to be world-locked to a position in the physical world, and a robot can use this positional understanding to navigate itself relative to its surroundings.
Of increasing value is the ability of the device to quickly orient itself or determine its own position relative to a three-dimensional coordinate space of the physical environment by efficiently loading the appropriate map data sets to accelerate the coarse relocalization step before proceeding to the more fine-grained localization step. A conventional method of self-orientation is to load all the map data sets of the physical environment into memory before the device starts to orient itself. However, this conventional method may be associated with practical disadvantages, including large memory requirements and long load times.